1. Field of the Invention
The present invention relates to a method and to a plant for rolling hot-rolled wide strip from continuously cast thin slabs or slabs of medium thickness of about 40 to 100 mm, wherein the cast slab strand is divided into sections, is subjected to a temperature treatment in a continuous furnace, and is conveyed for rolling into a rolling train.
2. Description of the Related Art
EP-A2 0 327 854 discloses a method and a plant for rolling initial strips cast on a continuous strip casting plant in a hot-rolling wide strip finishing rolling train, wherein the cast initial strips divided into initial strip lengths are subjected to a thermal treatment in a roller-hearth furnace in which a homogeneous rolling temperature is imparted to the initial strips. Immediately before entering the finishing rolling train, the initial strip lengths are descaled.
In the manufacture of thin slabs, it is frequently difficult to ensure the demanded surface quality over the entire length of the thin slab strand. Especially the first sections of the thin slabs cast at the beginning of casting or after a casting interruption may have deficiencies of the surface properties which will result in a quality reduction of the rolled sheet metal.
In order to eliminate this disadvantage, it is proposed in a not yet published German patent application (Serial No. P 196 21 259.6), to pull any slab sections which have deficiencies from the main production line, to carry out a surface treatment by grinding or by flame-treating, and subsequently to return the slab sections treated in this manner back into the main production line. For this purpose, the roller-hearth furnace, in which the slab sections are heated to a homogeneous rolling temperature, is formed over a partial length thereof by at least one portion which is transversely moveable into a side position, wherein the side position is in alignment with the surface treatment line. The slab sections to be treated are heated by this moveable furnace portion, are moved transversely into a side position of the roller-hearth furnace, are treated at their surfaces while being conveyed in longitudinal direction, are subsequently returned into the heating position on the side and are then returned in the heated condition transversely into the main production line. In accordance with this procedure, it is now possible to treat slab sections at their surfaces without interrupting the remaining production sequence.
The disadvantage of this known method is the fact that for carrying out the surface treatment it is necessary to install a separate processing line in which the slab sections must be moved forward and then again backward, wherein the apparatus required for this purpose is expensive and requires a large amount of space.